Hepatitis C virus promotes expression of the 3β-hydroxysterol δ24-reductase through Sp1
Article first published online: 16 MAR 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Medical Virology
Volume 84, Issue 5, pages 733–746, May 2012
How to Cite
Saito, M., Kohara, M. and Tsukiyama-Kohara, K. (2012), Hepatitis C virus promotes expression of the 3β-hydroxysterol δ24-reductase through Sp1. J. Med. Virol., 84: 733–746. doi: 10.1002/jmv.23250
- Issue published online: 16 MAR 2012
- Article first published online: 16 MAR 2012
- Manuscript Accepted: 16 JAN 2012
- Ministry of Health and Welfare of Japan
- Ministry of Education, Culture, Sports, Science and Technology of Japan
- Program for Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation
- Cooperative Research Project on Clinical and Epidemiological Studies of Emerging and Re-emerging Infectious Diseases
- oxidative stress
Hepatitis C virus (HCV) establishes chronic infection, which often causes hepatocellular carcinoma. Overexpression of 3β-hydroxysterol Δ24-reductase (DHCR24) by HCV has been shown to impair the p53-mediated cellular response, resulting in tumorigenesis. In the present study, the molecular mechanism by which HCV promotes the expression of DHCR24 was investigated. A significant increase in DHCR24 mRNA transcription was observed in a cell line expressing complete HCV genome, whereas no significant difference in the expression of DHCR24 was seen in cell lines expressing individual viral proteins. The 5′-flanking genomic region of DHCR24 was characterized to explore the genomic region and host factor(s) involved in the transcriptional regulation of DHCR24. As a result, the HCV response element (−167/−140) was identified, which contains AP-2α, MZF-1, and Sp1 binding motifs. The binding affinity of the host factor to this response element was increased in nuclear extracts from cells infected with HCV and corresponded with augmented affinity of Sp1. Both mithramycin A (Sp1 inhibitor) and small interfering RNA targeting Sp1 prevented the binding of host factors to the response element. Silencing of Sp1 also downregulated the increased expression of DHCR24. The binding affinity of Sp1 to the response element was augmented by oxidative stress, whereas upregulation of DHCR24 in cells expressing HCV was blocked significantly by a reactive oxygen species scavenger. Elevated phosphorylation of Sp1 in response to oxidative stress was mediated by the ATM kinase. Thus, activation of Sp1 by oxidative stress is involved in the promotion of expression of DHCR24 by HCV. J. Med. Virol. 84:733–746, 2012. © 2012 Wiley Periodicals, Inc.